Fasting and refeeding in the lactating dairy cow. 1. The recovery of milk yield and blood chemistry following a six-day fast

Effect of feed restriction on dairy cow milk production: a review

In the dairy cow, negative energy balance affects milk yield and composition as well as animal health. Studying the effects of negative energy balance on dairy cow milk production is thus essential. Feed restriction (FR) experiments attempting to reproduce negative energy balance by reducing the quantity or quality of the diet were conducted in order to better describe the animal physiology changes. The study of FR is also of interest since with climate change issues, cows may be increasingly faced with periods of drought leading to a shortage of forages. The aim of this article is to review the effects of FR during lactation in dairy cows to obtain a better understanding of metabolism changes and how it affects mammary gland activity and milk production and composition. A total of 41 papers studying FR in lactating cows were used to investigate physiological changes induced by these protocols. FR protocols affect the entire animal metabolism as indicated by changes in blood metabolites such as a decrease in glucose concentration and an increase in non-esterified fatty acid or β-hydroxybutyrate concentrations; hormonal regulations such as a decrease in insulin and insulin-like growth factor I or an increase in growth hormone concentrations. These variations indicated a mobilization of body reserve in most studies. FR also affects mammary gland activity through changes in gene expression and could affect mammary cell turnover through cell apoptosis, cell proliferation, and exfoliation of mammary epithelial cells into milk. Because of modifications of the mammary gland and general metabolism, FR decreases milk production and can affect milk composition with decreased lactose and protein concentrations and increased fat concentration. These effects, however, can vary widely depending on the type of restriction, its duration and intensity, or the stage of lactation in which it takes place. Finally, to avoid yield loss and metabolic disorders, it is important to identify reliable biomarkers to monitor energy balance.

A Comparative Review of the Extrinsic and Intrinsic Factors Regulating Lactose Synthesis

Milk is critical for the survival of all mammalian offspring, where its production by a mammary gland is also positively associated with its lactose concentration. A clearer understanding of the factors that regulate lactose synthesis stands to direct strategies for improving neonatal health while also highlighting opportunities to manipulate and improve milk production and composition. In this review we draw a cross-species comparison of the extra- and intramammary factors that regulate lactose synthesis, with a special focus on humans, dairy animals, and rodents. We outline the various factors known to influence lactose synthesis including diet, hormones, and substrate supply, as well as the intracellular molecular and genetic mechanisms. We also discuss the strengths and limitations of various in vivo and in vitro systems for the study of lactose synthesis, which remains an important research gap.

Aspects of transition cow metabolomics-Part II: Histomorphologic changes in the liver parenchyma throughout the transition period, in cows with different liver metabotypes and effects of a metaphylactic butaphosphan and cyanocobalamin treatment

The aims of this study were to evaluate histopathologic changes during the transition period, describe the histopathological features of the metabotypes identified in Part I (Schären et al., 2021b), and investigate effects of a metaphylactic treatment with butaphosphan and cyanocobalamin (BCC) on the liver parenchyma. Eighty German Holstein cows (mean 305-d production: 10,957 kg, range: 6,480-15,193 kg; mean lactation number: 3.9, range: 2-9) from a commercial dairy farm in Saxony, Germany, were enrolled in a randomized, prospective, triple-blinded study. Two groups received a treatment with BCC (5 or 10 mL/100 kg of body weight 10% butaphosphan and 0.005% cyanocobalamin, Catosal, Bayer Animal Health, n = 20 each) and one group a placebo treatment (NaCl 0.9%, n = 40). Liver biopsy specimens were collected 14 d antepartum (AP) and 7, 28, and 42 d postpartum (PP), routinely processed for histologic examination, and stained with hematoxylin and eosin, Sudan III, periodic acid-Schiff, and picrosirius red stains. The sections were assessed for fat and glycogen content and degenerative, inflammatory, fibrotic, and proliferative changes. The statistical analysis included the effects of the sampling day, the lactation number, the treatment, and the metabotype (A = medium, B = minor, C = large alterations in the liver metabolome profile between AP and PP status). There was mild to moderate fat infiltration in the liver of 37% of cows in the last 2 wk AP, and moderate to severe fat infiltration in 66% of cows in the first days PP. The degree of fat infiltration increased from 2 wk AP until the end of the first week PP, and then decreased until the end of the study period, at which time about 25% of cows had moderate to severe fatty infiltration. Lipidosis was positively correlated with the severity of liver cell degeneration, and negatively correlated with the degree of glycogen deposits. Complete glycogen depletion of hepatocytes was not observed in cows, even in the presence of severe hepatic lipidosis. Moderate to severe lymphocytic hepatitis was seen in 39% of cows throughout the study period, and cows with lactation numbers 5 or greater had perisinusoidal fibrosis more often than younger cows. Severe fibrosis and cirrhosis of the liver did not occur. Metabotype B animals exhibited a higher chance of fatty infiltration, lower glycogen storage, and perisinusoidal fibrosis and for this metabotype positive correlations were calculated between increased fat deposition in the liver and marked glycogen depletion, and increased degenerative, inflammatory, fibrotic, and proliferative changes of hepatic tissue. For the treatment with BCC, no significant effect was observed. In summary, during the transition period, the liver of dairy cows is characterized by fat accumulation and glycogen depletion and histologic signs of hepatitis and hepatocyte degeneration. These histomorphologic changes were accentuated in animals exhibiting little alterations in their liver metabolome profile across the transition period (metabotype B) and support the assumption of a decreased grass silage quality as a causative factor.

Effects of exogenous glucose on glucose metabolism in the lactating goat in vivo

1. Glucose turnover in fed and 48 h-starved lactating goats was determined during a glucose load of 500 μmol/min using a continuous infusion of [U-14C]- and [3-3H]glucose.

2. Endogenous rates of irreversible glucose turnover (i.e. total rates of irreversible glucose turnover minus the rate of exogenous glucose supply) were depressed during glucose loading by 14 and 62% in the fed and starved animals respectively.

3. Plasma glucose concentrations increased significantly by 57 and 88% in the fed and starved goats respectively. Plasma insulin concentrations increased by 108 and 128% in the fed and starved animals respectively.

4. Milk yields increased significantly (41%) in the starved animals during glucose loading, but were unaffected in fed animals.

5. In both the fed and 48 h-starved goats, mammary glucose metabolism via glycolysis and the pentose phosphate pathway appeared to be stimulated by glucose loading.

Feed restriction induces pyruvate carboxylase but not phosphoenolpyruvate carboxykinase in dairy cows

The ability of dairy cattle to adapt to changes in nutrient intake requires appropriately responsive expression of several key genes in liver. Holstein cows were used in 2 experiments to determine the effect of short-term feed restriction on expression of mRNA for gluconeogenic and ureagenic enzymes in liver. In experiment 1, cows were fed a total mixed diet for ad libitum intake for a 5-d period followed by 5 d of 50% of their previous 5-d ad libitum intake followed by 10 d of ad libitum feeding. Liver biopsies and blood samples were obtained on d 5, 10, and 20 of the experiment, the last day of each feeding period. Pyruvate carboxylase (PC) mRNA increased with feed restriction, but phosphoenolpyruvate carboxykinase (PEPCK) was unchanged. Expression of carbamoyl phosphate synthetase (CPS-I), argininosuccinate synthetase, and ornithine transcarbamylase mRNA were not altered by feed restriction; however, CPS-I mRNA expression tended to increase during realimentation. In experiment 2, cows were fed for ad libitum intake for 5 d and then fed 50% of previous intake for 5 d. Liver biopsy samples collected on d 5 and 10 were used for PC mRNA, PEPCK mRNA, and in vitro measure of gluconeogenesis from radiolabelled propionate and lactate. The data indicate expression of genes for key metabolic processes in liver of lactating cows is responsive to feeding level. Expression of PC mRNA is part of the adaptive response to feed intake restriction and is matched by increased capacity for gluconeogenesis from lactate.

Hyperlipemia and ketonuria in an alpaca and a llama

An alpaca and a llama in late stages of gestation were evaluated for lethargy, anorexia, and recumbency. Both camelids had cloudy, white, turbid serum, elevated serum triglyceride (1564, 5658 mg/dL, respectively) and cholesterol (158, 297 mg/dL, respectively) concentrations, and ketonuria. Signs of fetal stress were evident ultrasonographically in the alpaca, and a live cria was delivered by Cesarean section performed under general anesthesia. The alpaca developed severe metabolic acidosis, hepatic lipidosis, and acute renal failure secondary to renal lipidosis and died 36 hours after admission despite medical therapy. Histopathology revealed renal and hepatic lipidosis and neutrophilic pancreatitis. The cria died 72 hours after birth. The llama responded to IV electrolyte, dextrose, and regular crystalline insulin therapy. The pregnancy was maintained, and the llama was discharged from the hospital 20 days after admission. Two months after discharge, the llama gave birth to a live, 5 kg cria. Findings of hypertriglyceridemia, hypercholesterolemia, elevated sorbitol dehydrogenase activity, metabolic acidosis, azotemia, and ketonuria occurred in these two camelids. Based on this report, camelids appear to be similar to both horses and cattle in their response to severe energy imbalances in late gestation.

Blood chemistry of reindeer calves (Rangifer tarandus) during the winter season

1. Blood characteristics of reindeer calves fed on lichens were studied during the winter. 2. The serum total protein, albumin and globulin concentrations decreased during the winter, obviously partly due to protein deficiency in the diet. 3. High urea levels in autumn and midwinter were possibly reflections of increased stress and/or protein catabolism. 4. Marked lipolysis occurred in late winter, and thus increases were observed in fatty acids, glycerol, triglycerides and acetoacetate concentrations. 5. Serum sorbitol dehydrogenase (SDH) activity increased towards the spring, most probably reflecting changes in the liver. 6. A decrease in serum alkaline phosphatase (AP) activity occurred in midwinter due to cessation of growth. 7. It can be concluded that all the animals were at least in moderate condition throughout the winter and the physiological responses to a negative energy balanced reflected good adaptation.

Effects of moderate intensity treadmill exercise on triglyceride production in the laying fowl

1. Sustained aerobic exercise in domestic fowl has previously been shown to enhance lipid utilization by the skeletal muscles. The present study examined the possibility that such increased lipid oxidation in the laying female might lower the production of plasma triglycerides destined for transfer to the developing oocytes. 2. Following an intravenous injection of 25 muCi of 14C-labelled glycerol trioleate, the experimental birds performed 90 min of treadmill exercise at a work intensity approximately equivalent to 2.5 times the resting metabolic rate. 3. There was no evidence of either glycogen or triglyceride depletion in either the leg muscles or the viscera of the exercised birds. The specific activity of triglyceride TG-SRA found in the tissues was also the same in control and experimental birds. The time-course of the changes in plasma TG-SRA throughout the experimental period gave no indication that TG production had been affected by exercise. 4. It is concluded that the increased energy substrate demand arising from moderate-intensity, aerobic exercise is almost fully met by the liberation of fatty acids from adipose tissue TG stores, and has minimal impact on the hepatic manufacture of egg lipids.

Effect of prepartum energy, body condition, and sodium bicarbonate on health and blood metabolites of holstein cows in early lactation

Effects of prepartum energy and of postpartum sodium bicarbonate (0, .75% DM) on health were studied in two trials. In trial 1, 36 cows consumed either 102, 131, or 162% of their energy requirement in the dry period. Postpartum glucose and D(-)-3-hydroxybutyrate levels indicated that 131% group (between wk 1 and 2) and 162% group (over the first 4 wk) were closer to a ketotic state than treatment groups at other times. Displaced abomasums occurred more frequently in the 162% group than either the 102 or 131 group. Sodium bicarbonate did not alter the health. In trial 2, 40 cows were used to evaluate the effects of prepartum energy for a longer period. Energy treatments imposed in late lactation and in the dry period were 1) cows fed to requirement in both periods; 2) cows overfed in the first and underfed in the second period; 3) cows fed to requirement in the first and overfed in the second; 4) cows overfed in both periods. Blood metabolites and health measures were not affected by energy or sodium bicarbonate treatments. Overconsumption of energy by prepartum cows should be avoided; however, for a short period, overconsumption did not produce major health problems.